JP3121966B2 - Plate surface protective agent for lithographic printing plates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plate surface protective agent for a lithographic printing plate.

2. Description of the Related Art When making a lithographic printing plate, a so-called gum solution is applied in the final step. The purpose of applying the gum solution is not only to protect the hydrophilicity of the non-image area, but also to modify the image area such as adding or erasing it, to save it for the period from plate making until printing or to reuse it, and to attach it to a printing machine. The purpose of the present invention is to prevent dirt caused by the adhesion of fingerprints, oils and fats, dust and the like during and during handling, to protect against the occurrence of scratches, and to suppress the generation of oxidized dirt. Heretofore, as a gum solution for a lithographic printing plate, gum arabic, cellulose gum or an aqueous solution of a water-soluble polymer substance having a carboxyl group in a molecule has been generally used. However, these gum solutions have the following problems. That is, the gum solution is poured on the plate in the final finishing step of the normal printing plate, and this is sponge,
Alternatively, the entire surface of the printing plate is spread with a cotton tampon or the like, and further rubbed with a wiping cloth until the printing plate is dried. At this time, the water-soluble polymer substance is partially thickened in the image area (ink receiving area).
The image portion of the thickly applied portion has a poor ink adhesion in the printing process, and requires a considerable number of imprints to obtain a printed material having a desired ink density. Generally, this phenomenon is referred to as printing omission (so-called poor inking). When the above phenomenon occurs, the plate is generally washed with water or a weakly acidic solution to reproduce the missing image area,
It is necessary to remove hydrophilic colloid adsorbed on the image area. Since this washing step takes time, a gum removing solution described in Japanese Patent Publication No. 56-19277 has also been developed.

On the other hand, in order to protect the oil sensitivity of the image area, it is often practiced to coat the image area with fats and oils before gumming, but this complicates the process and reduces workability. It is not preferable because of waste liquid contamination and health problems. For this reason, attempts have been made to use a water-soluble organic polymer compound that does not cause printing omission as a plate surface protective agent. For example, JP-A-52-56603, JP-A-54-97102, West German Patent No. 2,504,594, and Soviet Patent No. 623,755 disclose dextrin, pullulan and pullulan derivatives, carboxy-containing polyacrylamide derivatives, methyl (meth) acrylate graft poly. Acrylamide copolymers and the like have been proposed. In addition, starch modified compounds such as carboxymethylated modified starch and cyclodextrin are also shown,
In any case, since the desensitizing power of the non-image area is not sufficient, the non-image area is currently mixed with gum arabic. Furthermore, compared to gum arabic, the use of the emulsion has been limited due to its unstable suitability for protective colloid. On the other hand, gum arabic is produced mainly in Sudan, which is said to be the Arabian gum belt area of the continent of Africa, but in recent years, market fluctuations have been severe due to drought caused by climate change and political instability. Is getting harder. For this reason,
There has been a demand for the development of an alternative polymer.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a plate surface protective agent which renders non-image areas of a lithographic printing plate insensitive to oil and at the same time, does not cause printing omission even when stored for a long period of time. . Another object of the present invention is that the lithographic printing plate can be easily applied to the plate by using a sponge, a cotton tampon, an automatic gum coater or the like, and can be easily washed from water or brought into contact with a humidifying roller of a printing machine from a lithographic printing plate. It is an object of the present invention to provide a plate surface protective agent which can be removed in a non-image area, can maintain the hydrophilicity of the non-image area, and can be used without adding gum arabic.

[0004]

Means for Solving the Problems The inventors of the present invention have made intensive studies to achieve the above object, and have accomplished the present invention. That is, the present invention is an emulsification type plate surface protective agent for a lithographic printing plate comprising an aqueous solution containing a water-soluble soybean polysaccharide having a film forming property. The water-soluble soybean polysaccharide is a polysaccharide obtained by extracting raw soybean with water, and mainly contains galactose, arabinose, and galacturonic acid as constituents. Commercial products include Soyafive-S-LN (manufactured by Fuji Oil Co., Ltd.). The average molecular weight of the soybean polysaccharide that can be used in the present invention is preferably 50 to 100,000, and the viscosity (25 ° C) of a 10% by weight aqueous solution in the range of 5 to 100 cp is preferably used. The content of the soybean polysaccharide in the plate surface protective agent for a lithographic printing plate of the present invention is preferably from 0.3 to 50% by weight, more preferably from 0.5 to 40% by weight. These soybean polysaccharides are dissolved in water or warm water and used as a uniform aqueous solution. In the present invention, the soybean polysaccharide may be mixed with another starch such as dextrin or modified starch. Further, another water-soluble polymer compound may be added. For example, gum arabic, cellulose derivatives (eg, carboxymethylcellulose, carboxyethylcellulose, methylcellulose, etc.) and modified products thereof, polyvinyl alcohol and its derivatives polyvinylpyrrolidone, polyacrylamide and its copolymers, vinyl methyl ether / maleic anhydride copolymer , Vinyl acetate / maleic anhydride copolymer, styrene / maleic anhydride copolymer, and the like.

In general, it is more advantageous to use the plate surface protective agent of the present invention in the acidic range of pH 3 to 6. pH 3 ~
In order to obtain 6, a mineral acid, an organic acid or an inorganic salt is generally added to the plate surface protective agent. The added amount is 0.01
~ 2% by weight. For example, mineral acids include nitric acid, sulfuric acid, phosphoric acid, and metaphosphoric acid. Examples of the organic acid include citric acid, acetic acid, oxalic acid, malonic acid, p-toluenesulfonic acid, tartaric acid, malic acid, lactic acid, levulinic acid, phytic acid, and organic phosphonic acid. Examples of the inorganic salt include magnesium nitrate, monobasic sodium phosphate, dibasic sodium phosphate, nickel sulfate, sodium hexametaphosphate, sodium tripolyphosphate and the like. Mineral acids,
At least one kind or two or more kinds of organic acids or inorganic salts may be used in combination.

The surface condition of the coating layer is improved by adding a surfactant to the plate surface protective agent of the present invention. Surfactants that can be used include anionic surfactants and / or nonionic surfactants. For example, anionic surfactants include fatty acid salts, abietic acid salts, hydroxyalkanesulfonates, alkanesulfonates, dialkylsulfosuccinates, linear alkylbenzenesulfonates, branched alkylbenzenesulfonates, alkylnaphthalene sulfones Acid salts,
Alkylphenoxy polyoxyethylene propyl sulfonates, polyoxyethylene alkyl sulfophenyl ether salts, N-methyl-N-oleyl taurine sodium, N-alkyl sulfosuccinic acid monoamide disodium salt, petroleum sulfonates, sulfated castor oil,
Sulfated tallow oil, sulfates of fatty acid alkyl esters, alkyl sulfates, polyoxyethylene alkyl ether sulfates, fatty acid monoglyceride sulfates, polyoxyethylene alkyl phenyl ether sulfates, polyoxyethylene styryl phenyl sulfate Ester salts, alkyl phosphate salts, polyoxyethylene alkyl ether phosphate salts, polyoxyethylene alkyl phenyl ether phosphate salts, partially saponified styrene-maleic anhydride copolymers, olefin-maleic anhydride copolymers Partially saponified compounds, naphthalene sulfonate formalin condensates, and the like are included. Of these, dialkyl sulfosuccinates, alkyl sulfates and alkyl naphthalene sulfonates are particularly preferably used.

[0007] Nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene polystyryl phenyl ether, polyoxyethylene polyoxypropylene alkyl ether, and glycerin fatty acid partial ester. , Sorbitan fatty acid partial esters,
Pentaerythritol fatty acid partial esters, propylene glycol monofatty acid ester, sucrose fatty acid partial ester, polyoxyethylene sorbitan fatty acid partial ester, polyoxyethylene sorbitol fatty acid partial ester, polyethylene glycol fatty acid ester,
Polyglycerin fatty acid partial esters, polyoxyethylenated castor oil, polyoxyethylene glycerin fatty acid partial esters, fatty acid diethanolamides, N,
Examples include N-bis-2-hydroxyalkylamines, polyoxyethylene alkylamines, triethanolamine fatty acid esters, and trialkylamine oxides. Among them, polyoxyethylene alkyl phenyl ethers, polyoxyethylene-polyoxypropylene block polymers and the like are preferably used. In addition, fluorine-based or silicon-based anionic or nonionic surfactants can be used in the same manner. Two or more of these surfactants can be used in combination. For example, a combination of two or more different anionic surfactants or a combination of an anionic surfactant and a nonionic surfactant is preferable. The amount of the surfactant used does not need to be particularly limited, but is preferably
It is 0.01 to 20% by weight.

[0008] In addition to the above components, if necessary, lubricants such as ethylene glycol, propylene glycol, triethylene glycol, butylene glycol, hexylene glycol, diethylene glycol, dipropylene glycol,
Glycerin, trimethylolpropane, diglycerin and the like are preferably used. These wetting agents may be used alone or in combination of two or more. Generally, it is preferred that the wetting agent be used in an amount of 1 to 25% by weight. Further, a chelating compound may be added to the plate surface protective agent of the present invention.

Usually, the plate surface protective agent is commercially available as a concentrated solution, and is diluted with tap water, well water or the like at the time of use. Calcium ions and the like contained in the diluted tap water and well water have an adverse effect on printing and may cause the printed matter to be easily stained. Therefore, by adding a chelate compound, the above-described disadvantage can be solved. . Preferred chelating compounds include, for example, ethylenediaminetetraacetic acid, its potassium salt, its sodium salt; diethylenetriaminepentaacetic acid, its potassium salt, its sodium salt; triethylenetetraminehexaacetic acid, its potassium salt, its sodium salt, hydroxyethylethylenediaminetriacetic acid Acetic acid, its potassium salt, its sodium salt; nitrilotriacetic acid, its sodium salt; 1-hydroxyethane-1,1-diphosphonic acid, its potassium salt, its sodium salt; aminotri (methylenephosphonic acid), its potassium salt, Organic phosphonic acids such as sodium salts and phosphonoalkanetricarboxylic acids can be mentioned. Organic amine salts are also effective in place of the sodium and potassium salts of the above chelating agents. These chelating agents are selected from those which are stably present in the composition of the plate surface protective agent and do not inhibit printability. The amount of addition is suitably 0.001 to 1.0% by weight based on the plate surface protective agent at the time of use.

Further, a preservative, an antifoaming agent and the like can be added to the plate surface protective agent of the present invention. For example, as a preservative, phenol or a derivative thereof, formalin, an imidazole derivative, sodium dehydroacetate, a 4-isothiazolin-3-one derivative, a benzoisothiazolin-3-one,
Benztriazole derivatives, amiding anidine derivatives, quaternary ammonium salts, pyridine, quinoline, derivatives such as guanidine, diazine, triazole derivatives,
Oxazole, oxazine derivatives and the like. A preferable addition amount is an amount stably exerting an effect on bacteria, mold, yeast and the like, and varies depending on the kind of bacteria, mold and yeast, but is 0.01 to the plate surface protective agent at the time of use. ~
It is preferably in the range of 4% by weight, and it is preferable to use two or more preservatives in combination so as to be effective against various molds and sterilization. In addition, a silicone antifoaming agent is preferable as the antifoaming agent. Among them, any of emulsification dispersion type and solubilization can be used. Preferably, the surface protective agent at the time of use is 0.0.
The optimal range is from 01 to 1.0% by weight.

[0011] In addition to the above components, a sensitizer may be added to the plate surface protective agent of the present invention, if necessary. For example, turpentine oil, xylene, toluene, loheptane, solvent naphtha, kerosene, mineral spirit, boiling point of about 1
Hydrocarbons such as petroleum fractions at 20 ° C to about 250 ° C, such as dibutyl phthalate, diheptyl phthalate, di-n
Phthalic acid diester agents such as octyl phthalate, di (2-ethylhexyl) phthalate, dinonyl phthalate, didecyl phthalate, dilauryl phthalate and butylbenzyl phthalate, for example dioctyl adipate;
Butyl glycol adipate, dioctyl azelate,
Aliphatic dibasic acid esters such as dibutyl sebacate, di (2-ethylhexyl) sebacate, dioctyl sebacate, for example, epoxidized triglycerides such as epoxidized soybean oil, for example, tricresyl phosphate, trioctyl phosphate, tris A plasticizer having a freezing point of 15 ° C. or less and a boiling point at 1 atm of 300 ° C. or more, such as a phosphoric acid ester such as chloroethyl phosphate, for example, a benzoic acid ester such as benzyl benzoate, is included.

Further, together with these solvents, for example, ketones such as cyclohexanone, halogenated hydrocarbons such as ethylene dichloride, ethylene glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monophenyl ether, ethylene glycol monobutyl ether, etc. Also, preferred fatty acids include caproic acid, enanthic acid, caprylic acid, helargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, heptadecylic acid, stearic acid, nonadecanoic acid, araquine Acid, behenic acid, lignoceric acid, cerotic acid, heptacosanoic acid, montanic acid, melicic acid, lacceric acid,
Saturated fatty acids such as isovaleric acid and acrylic acid, crotonic acid,
Isocroton, undecylenic acid, oleic acid, elaidic acid, setleic acid, nilucic acid, butesidic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, propiolic acid, stearolic acid, succinic acid, tallic acid, ricanoic acid, etc. There are saturated fatty acids. More preferably 50 ° C
Is a liquid fatty acid, more preferably 5 to 25 carbon atoms, most preferably 8 to 2 carbon atoms.
It is one. These sensitizers can be used alone or in combination of two or more. The preferred range of the amount used is 0.01 to 10% by weight of the plate surface protective agent, and the more preferred range is 0.0.
5 to 5% by weight. The above sensitizers may be prepared by emulsifying and dispersing the plate surface protective agent of the present invention in an emulsified dispersion type, and may be contained as an oil phase thereof, or may be solubilized with the aid of a solubilizer. .

The plate surface protective agent using the soybean polysaccharide of the present invention is of an emulsifying type, and exhibits an excellent effect of protecting oil sensitivity in image areas and hydrophilicity in non-image areas. The plate surface protective agent of the present invention can be used for both positive type lithographic printing plates and negative type lithographic printing plates. Further, even if an automatic gum filling machine or the like is used, the coating can be performed uniformly. The treatment with the plate surface protective agent of the present invention can be carried out immediately after the development treatment step by anhydrous washing, after the development treatment (including a washing step, running water circulating washing or a small amount of rinsing with water) or containing a surfactant. It can also be carried out after treatment with a rinse solution. At the time of printing, it is possible to obtain a sufficiently satisfactory clear print immediately after printing without producing many defective prints as in the related art. The soybean polysaccharide which is a main component of the plate surface protective agent of the present invention is a processing agent for various lithographic printing plates other than the plate surface protective agent, for example, a plate surface detergent, an emulsified developing ink dampening solution,
It can also be used for rinsing liquid, erasing liquid and the like.

[0014]

The present invention will be described in detail with reference to the following examples. The plate surface protective agents of the following Example 1 and Comparative Examples 1 and 2 were each diluted 1: 1 with water to obtain working solutions. A lithographic printing plate (FPS Fuji Photo Film Co., Ltd., anodized multi-grain type positive PS plate) is image-exposed and developed by a PS automatic developing machine 900D using a positive developer having the following composition. A protective agent was applied. (Developer): Sodium silicate (SiO ₂ / Na ₂ O molar ratio is 1.2) 2 g: Sodium ethylenediaminetetraacetate 4H ₂ O 0.1 g: Water 97.9 g

The lithographic printing plate, to which each plate surface protective agent has been applied and the plate making has been completed, is divided into two parts, stored under the conditions shown in Table 1 , printed using a Heidel SOR printing machine, and evaluated according to the performance evaluation method shown in Table 2. The performance was evaluated.

[0016]

[Table 1] Storage conditions A Indoor B Compulsory storage Temperature 45 ° C / Humidity 80% RH 24 hours

[0017]

[Table 2] Item Test conditions and method 1 Ink adhesion The number of sheets of paper from the start of printing until the ink completely adheres to the image area and a normal print is obtained. 2 Blanket stain After printing 1,000 sheets, the degree of ink adhesion in the non-image area on the blanket was visually determined. 3. Oil stains A liquid of 1 g of oleic acid and 50 g of xylene was dropped on the non-image portion in an amount of 50 μl, and the non-image portion was examined for stain. 4 Scratch dirt Scratch tester of Shinto Kagaku Co., Ltd. 0.3R diamond needle Load 20g 50g 75g 100g 150g 200g The plate is scratched with 200g, and the presence or absence of stain on each plate is examined.

[0018]

Example 1 Water-soluble soybean polysaccharide (Soya Five manufactured by Fuji Oil Co., Ltd.)
S-LN: analysis value: galactose 43.6%, arabinose
(22.5%, galacturonic acid 2.2%, residual protein 4.7%) 8
0 parts by weight and 170 parts by weight of cream dextrin in pure water 6
It dissolved in 73.8 parts by weight. 5.0 parts by weight of monoammonium phosphate, 3 parts by weight of phosphoric acid, methyl benzoate
0.2 parts by weight, 4-isothiazolin-3-one derivative 1.0
A part by weight was added and dissolved to prepare an aqueous phase. 10 parts by weight of DOP (dioctyl phthalate), benzyl alcohol 5.
0 parts by weight, di (2-ethylhexyl) as a surfactant
Sulfosuccinate (Lapisol B-80 NOF Corporation)
25 parts by weight of polyoxyethylene nonylphenol ether (Emulgen # 903 manufactured by Kao Corporation, HLB =
7.8) 12 parts by weight and 3 parts by weight of sorbitan monooleate (Nonion OP-80 manufactured by NOF Corporation) were mixed and dissolved to prepare an oil phase. The aqueous phase was stirred at 500 to 600 rpm, and the oil phase was added dropwise little by little. After the completion of the addition, the mixture was passed through a homogenizer to obtain an emulsified plate surface protective agent. Table On the other hand as a comparison
The plate surface protective agents of Comparative Examples 1 and 2 shown in No. 3 were prepared . The emulsion stability was observed after storage in a room (25 ° C., 72 hours) and after freezing and thawing (freezing at −15 ° C., 72 hours). Table 4 shows the results.

[0020]

[Table 3] Comparative Example 1 Comparative Example 2 Pure water 673.8 g 673.8 g Cream dextrin 170 170 Water gum arabic 80- ^* Pinestar S-80 Primary ammonium phosphate 55 phase Phosphoric acid (85%) 33 Methyl benzoate 0.2 0.2 4- Isothiazolin-3-one derivative 1.0 1.0 DOP 10.0 10.0 Oil Benzyl alcohol 5.0 5.0 Lapisol B-80 25.0 25.0 Phase Emulgen # 903 12.0 12.0 Nonionic OP-80 3.0 3.0 Pinestar S: A modified starch product manufactured by Matsutani Chemical Co., Ltd.

[0021]

[Table 4] Example 1 Comparative Example 1 Comparative Example 2 Storage Conditions A B A B A B Ink adhesion (sheets) 7 to 10 7 to 10 20 to 30 40 to 50 7 to 10 7 to 10 Blanket stain ○ ○ ○ ○ × × Oil stain ○ ○ ○ ○ △ △ Scratch stain 150-150-150- 150 ~ 50g 50g 200g 200g 200g 200g ○ ○ ○ ○ × × Emulsification room Indoor ○ ○ △ Qualitative Freezing and thawing ○ ○ △ Separation of upper layer × ：: good Δ: slightly poor ×: poor As shown in the above table, the plate surface protective agent of the present invention had extremely satisfactory performance as compared with those of the comparative examples.

According to the present invention, the ink is excellent in the inking property, the hydrophilicity of the non-image area can be maintained, and the emulsion stability is excellent.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-6-191175 (JP, A) JP-A-63-191693 (JP, A) JP-A-62-111692 (JP, A) JP-A-62-16992 9995 (JP, A) JP-A-59-57793 (JP, A) JP-A-58-25995 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B41N 3/08 G03F 7 / 40 502

Claims (1)

(57) [Claims] An emulsion type lithographic printing plate surface protective agent comprising an aqueous solution containing a water-soluble soybean polysaccharide having a film forming property.